Measurement of stopping power of 240 MeV argon ions in partially ionized helium discharge plasma

Abstract

An energy loss of 240 MeV argon ions in a Z-pinch helium plasma has been for the first time observed throughout the entire pinching process. Standard Stark broadening analysis gives an electron density ranging from 4 to 6 × 1017 cm−3 during the pinch. To deduce stopping power from the energy loss, the target thickness of the helium plasma has been evaluated assuming the mean charge of helium based on thermal equilibrium. The observed electron density and the mean charge of helium give a target thickness of 30 ± 3 μg cm−2 from 1 μs to 1.8 μs after the discharge ignition. The measured stopping power exceeds a tabulated value for cold helium gas by a factor of 2 to 3 around the time of the first pinch. The experimental stopping power is compared with theoretical values calculated using an equation of stopping power for a partially ionized plasma.

Dynamic screening and charge state of fast ions in plasma and solids

“…The topic of the charge state and energy loss of energetic ions penetrating matter, be it at ambient conditions or in the plasma state, has been a subject of very extensive and longstanding experimental and theoretical research (Deutsch et al, 1989;Dietrich et al, 1992;Gardes et al, 1988;Hoffmann et al, 1990;Kojima et al, 2002;Nardi et al, 2007;Nardi & Zinamon, 1982;Ogawa et al, 2000;Sigmund & Narmann, 1995;Stockl et al, 1996). Since the advent of intense proton and light ion beams generated by intense lasers, this field has experienced a renaissance due to applications ranging from inertial fusion with fast ignition to medical applications (Barriga-Carrasco, 2008;Cook et al, 2008;Eliezer et al, 2007;Evans, 2008;Flippo et al, 2007;Hora, 2007;Romagnani et al, 2008).…”